What is a direct antiglobulin test (DAT)?

Updated: Jun 25, 2020
  • Author: Julie Katz Karp, MD; Chief Editor: Jun Teruya, MD, DSc, FCAP  more...
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Answer

Answer

The direct antiglobulin test (DAT) is used to determine whether red blood cells (RBCs) have been coated in vivo with immunoglobulin, complement, or both. The direct antiglobulin test is sometimes colloquially referred to as the direct Coombs test, because it is based on a test developed by Coombs, Mourant, and Race. [1]

By way of comparison, the indirect antiglobulin test (IAT), colloquially referred to as the indirect Coombs test, is used to determine the presence of antibody in the serum or plasma. [2]

A schematic of the direct antiglobulin test (DAT) A schematic of the direct antiglobulin test (DAT) and the indirect antiglobulin test (IAT). Courtesy of Wikipedia.

There are many causes of a positive direct antiglobulin test.

Depending on the technique and the reagents used, a positive direct antiglobulin test has been reported in 1:1000 to 1:14,000 blood donors and 1%-15% of hospital patients. Most blood donors with positive direct antiglobulin test results appear healthy, and most show no overt signs of hemolytic anemia. [3]

It is important to remember that a positive direct antiglobulin test is neither 100% sensitive nor specific for hemolytic anemia.

The clinical significance of a direct antiglobulin test result should take into consideration the patient's clinical history, diagnoses, and other laboratory test results.

The direct antiglobulin test is used most commonly to investigate possible hemolytic transfusion reactions, hemolytic disease of the fetus and newborn (HDFN), autoimmune hemolytic anemia, and drug-induced immune hemolysis. [4, 5]


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